Hydroelectric energy is one source of so-called renewable energy. Referring to FIG. 1, about 48% or almost half of all electric energy is produced by steam generation using coal. Natural gas provides about 18% of U.S. electric energy, and nuclear energy now provides about 22% via steam generation. Petroleum, such as oil, is used to produce only about 1% of U.S. electric energy. Coal, natural gas and petroleum are carbon-based and when burned produce emissions which can be costly to mitigate or, if not mitigated, can be dangerous or at least increase the so-called carbon footprint in the earth's atmosphere. The supply of coal, gas and petroleum is also limited. Nuclear energy generation, unless handled with extreme care, is dangerous, and the spent nuclear fuel becomes a hazard to the world.
Consequently, the hope of electrical energy generation for the future is in so-called renewables which include, but are not limited to, the air (wind power), the sun (solar power) and water (hydroelectric) sources. The great Hoover dam and the Tennessee Valley Authority are exemplary of projects started in the early 20th century in the United States. Large hydro-electric turbines in such dams on rivers in the United States are now being replaced with more efficient and larger capacity turbines. But the number and utility of dam-based hydroelectric power is limited, and the dams shut down commercial river traffic on navigable rivers. The dam backs up a river to form a lake which can take away valuable land resources that could be used to grow food or permit animals to feed. On the other hand, the created lakes provide water control and recreational use for boating, fishing and the like. Nevertheless, there remains a need for a device that may save the cost of building a dam, permit the hydroelectric generation of electricity and use the inherent flow of a river or the flow of ocean currents, tides and waves.
Referring to FIG. 2, it may be seen that so-called biomass energy generated from plant and animal material (waste), while it amounts to 5.83% of total renewable energy, has similar problems to those of non-renewable carbon-based systems and can cause emissions. While hydro-electric energy amounts to the next greatest renewable source at 3.96%, it is believed that more can be done to efficiently utilize the rivers, tides and ocean currents in the United States and near its shores than by hindering the flow of water commerce by the construction of dams.
Other renewable sources include geothermal, wind and solar energy. While these are “clean” sources, to date, their growth has been unimpressive. Only wind energy is supported by the Department of Energy to grow from 0.55 to 20% of all US energy in approximately 20 years.
Referring to FIG. 3, there is shown a currently used conventional wind turbine 300. Further detail of a conventional turbine is described in WO 1992/14298 published Aug. 20, 1992 and assigned to U.S. Windpower, Inc. A variable speed rotor 305 may turn a gearbox 312 (upper black and white drawing) to increase the rotational velocity output of the rotor and blade assembly 305, 307, 309. For example, a so-called cut-in speed (rotational velocity) of a rotor 305 may be about six revolutions per minute and the rotor blade may typically cut-out at about 30 revolutions per minute by controlling the pitch of the rotor 305 via a pitch control system 307 during conditions of high wind velocity and to reduce rotor blade noise. Typically, wind speeds over 3 meters/sec are required to cause the large rotor blades to turn at the cut-in speed (rotational velocity). Wind frequency between cut-in and cut-out speeds (velocities) has been measured to vary depending on location, weather patterns and the like. Placement high on a hill or a mountain of a wind turbine, for example, may be preferable to locating the wind turbine at a low point in a valley. Consequently, it may be recognized that there are periods of time when wind turbines 300 do not have sufficient wind speed to operate at all depending on weather conditions, placement and the like.
When wind speed reaches an excess amount, a pitch (and yaw) control system 307 may measure the wind speed and adjust the pitch of rotor blades 305 to pass more wind and so control the rotor blade from turning too fast as well as point the rotor blade into the wind. Yaw control may supplement pitch control to assist in pointing a rotor into the direction of flow. Noise from rapid rotor velocity can be abated, for example, by turning the blade parallel to the wind using a wind speed control system to thus maintain the rotational velocity close to a cut-out speed. An anemometer 380 at the tail of the turbine 300 may measure wind velocity and provides a control input. The tail of the turbine may be equipped with a rudder or wind vane for pitch or yaw control. Horizontal or vertical stabilizers (not shown) may be provided for pitch or yaw control. The rudder or wind vane may help point the variable speed rotor 305 into the wind. In general, however, there is a problem with known wind turbine systems that only a portion of the wind energy available at a site of a wind turbine farm may be harnessed resulting in harnessing only a portion of the kinetic energy of the available wind to feed a power grid.
Referring again to FIG. 3, the gearbox 312 may multiply the cut-in speed (rotor output) of six RPM, for example, by fifty yielding 300 RPM (more or less) for turning a variable speed generator 314 (upper black and white line drawing). A variable speed generator 314 may be used to convert the varying rotational speed of a main shaft 309 (upper black and white line drawing) to a variable frequency alternating current 322 for input to a power converter called a variable frequency converter 320 (VFC 320). In so doing, the variable frequency alternating current power 322 may be converted to direct current 324 and then to irregularly switched alternating current power 326 at a useful frequency such as 60 Hz. The conversion from variable frequency to direct current to constant frequency introduces inefficiency in converting kinetic energy (flow energy) to useable electric energy and so reduces an amount of power that may be output to grid 330.
VFC 320 converts variable frequency alternating current 322 produced by variable speed generator 314 to direct current DC 324, to irregular switched alternating current 326. The irregular switched alternating power 326 is acceptable for outputting to grid 330 of constant power alternating current at constant frequency 328 but is inefficiently produced. The VFC (power converter) 320 frequently fails. The cost to replace known variable frequency converters (power converters) 320 is, for example, between $50,000 and $100,000 and, consequently, an alternative design has been sought for the conventional wind turbine 300 as will be further discussed herein with reference to FIGS. 4 and 5.
A gearbox 312 is known to have a failure rate of approximately 5%. Electronics used in a wind turbine 300 has the highest potential failure rate of 26%. Control units generally exhibit a failure rate of 11%. Sensors and yaw control exhibit approximately a 10% failure rate. The failure rate of VFC 320 may be on the order of 26% (electronics) according to an ongoing consortium's study of drive train dynamics at the University of Strathclyde, Glasgow, Scotland. The mean time between failures may be only two years on average; and the replacement cost may be over $50,000 (US) per converter. A failure rate of the generator 314 is on the order of 4.5%. Consequently, problems related to known wind turbines relate closely to the failure rate of gearboxes, generators, variable frequency converters and associated electronics and inefficiencies of operation.
A solution to the identified problems is to provide a constant rotational velocity as an input to the constant speed electric generator so that the generator in turn can produce a constant frequency output and deliver the power directly to grid 330. Transmissions have been developed or are under development by the following entities: IQWind, Fallbrook and Voith Wind (Voith Turbo) to provide a constant output from a variable input. U.S. Pat. No. 7,081,689, (the '689 patent) assigned to Voith Turbo of Germany is exemplary of an overall system control design providing three levels of generator control. Voith provides a so-called power split gear and a hydrodynamic Fottinger speed converter or transformer adapted to be connected between a rotor and gear assembly and a synchronous generator for outputting power to a grid, for example, at 50 Hz (European).
Many of the problems of wind turbines are carried forward into run-of-the-river and tidal turbines. There is the same problem of having to convert a variable frequency input to a constant frequency output. On the other hand, the density (mass) of water is much greater and its speed is not as variable as wind speed. Generally, rivers flow in one direction and the major ocean currents do the same. Wave generation, however, in oceans and other large bodies of water varies with wind and weather. Ocean shore waves are more predictable and a strong undertow can be useful for electric power generation.
Referring now to FIG. 4, there is shown a concept for improving wind turbines by use of a mechanical direct drive 400 in which rotor designated 405 and shaft 409 drive generator 414. A direct drive may be used to directly drive an electric generator without using a gearbox, i.e. directly driving the generator. The failure and efficiency problems of gearboxes may be eliminated by eliminating the gearbox with direct drive. One may increase the number of poles by fifty times, use power converters 320 and so result in reduced down time for repairs at the expense of increased cost due to the direct drive assembly 400. A speed converter to convert variable speed to constant speed is disclosed in U.S. Pat. No. 8,388,481 which is entirely mechanical and so improves upon the high failure rate, reliability and efficiency of known electrical/mechanical systems. Speed converters under development are shown in FIG. 5 which may be described as infinitely variable speed converters.
Referring to FIG. 5, a belt and pulley driven continuously variable transmission (CVT) is known but is dependent on friction drive and is not scalable. Traction drive infinitely variable transmissions are known produced by Torotrak and Fallbrook. The Fallbrook device may be described by U.S. Pat. No. 8,133,149. A 2004 report, NREL/TP-500-36371, concluded that the Fallbrook device is not scalable. Further speed converters are described by FIGS. 10 and 11 of U.S. Pat. No. 8,641,570 of Differential Dynamics Corp. (also known as DDMotion). The DDMotion speed converters are differentiated from those of Torotrak and Fallbrook by their gear drives (no pulleys or belts) and that they are scalable. Now, known river and ocean devices will be discussed with reference to FIGS. 6 to 11.
PRIOR ART FIG. 6 shows a line drawing of a turbine produced by Hydrovolts, Inc. The depicted apparatus 600 appears to comprise a waterwheel 610 and may comprise a gear and belt drive (inside the box, not shown) which may, because of the belt, be susceptible to slippage. At their web site, a 15 kW waterfall turbine is described for use at a waterfall such as at spillways or outflows in industrial plants. Hydrovolts also produces a 12 kW zero-head canal turbine that allegedly can capture the energy in moving water. Reference may be made to U.S. Published Patent Application 2010/0237626 of Hammer published Sep. 23, 2010, which appears to comprise a waterwheel construction. Hydrovolts' rotating (hinged) blades may control some of the water flow speed, but it is urged that the rotating blades may be susceptible to damage.
Referring now to FIG. 7, there is provided a mechanical perspective view of a river turbine 700 attributed to Free Flow Power Corp. and may have been lowered to the bottom of the Mississippi River or attached to a piling. It is believed that the device 700 comprises a device 720 very similar to a turbine engine of an airplane but below water level and the water, at velocity, drives a turbine propeller 710. Due to lowering prices of natural gas, the project became economically unviable (according to their press release in 2012).
It is generally known in the art to utilize devices that look much like wind turbines to capture water energy. Referring to FIG. 8, there is shown a mechanical diagram of a tidal and/or river current turbine taken from FIG. 1 of U.S. Pub. Patent App. 2009/0041584. The diagram provides the labels, showing direction of water flow “A” (from right to left). Note that the turbine rotates on a pole so that rotor blade 150 captures the water as it passes. This device is available from Verdant Power and may be further described by U.S. Published Patent Application 2009/0041584 of Feb. 12, 2009. It is respectfully submitted that Verdant Power may currently be strengthening their blades and adding pitch control.
Referring to FIG. 9, there is shown a mechanical front view of a rotating ring device 900 including rotating ring 910 available from Oceana Energy Company. This turbine drawing taken from FIG. 1 of U.S. Published Patent Application 2012/0211990 allegedly comprises hydrofoils both external and internal to the rotating ring. The device may be further described by Oceana Energy's U.S. Published Patent Application 2012/0211990 of Aug. 23, 2012.
Perhaps the most like a wind turbine in appearance is the tidal energy turbine 1000 of ScottishPower Renewables, a division of Iberdrola. According to press releases, this tidal device 1000 with its propeller (rotor blades) 1010 is capable of generating approximately 10 MW of power as an “array” perhaps of twelve or more such devices at less than 1 MW each.
Devices are also known for harnessing the power in water waves such as ocean waves. Such a device is known and available from Pelamis Wave Power. Referring to FIG. 11A taken from FIG. 1 of Pelamis's U.S. Pub. Patent Application 2013/0239566, a Pelamis device 10 floats in the ocean, the device 10 may comprise a plurality of hinged sections 12-A, 12-B, 12-C, 12-D and 12E. Referring to FIGS. 11B and 11C, there is shown the direction of a wave from left to right. As the wave passes through the hinged sections, the sections 12A through 12E move up and down with the height of the wave. The wave thus creates movement which may be used to generate electricity. It may be said that the higher the wave, the greater the movement; the calmer the seas, the less the movement. Further details are provided in U.S. Published Patent Appl. No. 2013/0239566 of Sep. 19, 2013.
Referring now to FIG. 12, there is a map of the United States showing the major rivers which include the Ohio, the Mississippi, the Missouri, the Snake River and the Pecos and Brazos Rivers of Texas. As can be seen from the map, there is a great potential to harness the water energy of these rivers in the United States and to power, for example, the entire area covered by the Mississippi River and its tributaries including the Missouri, the Platte and the Red Rivers. Using dams would be costly. It may be that only Free Flow Power (FIG. 7) has developed a device for use on such a river as the Mississippi (but Free Flow Power abandoned the Mississippi project in 2012).
Referring to FIG. 13, there is shown a map of the world showing the major rivers of the world, further highlighting the potential to harness water energy in rivers world-wide. Finally, referring to FIG. 14, there is shown a map of the oceans showing major ocean currents. Proximate to the United States, there is the strong ocean current of the gulf stream current 1401 which is known to flow northward along the east coast of the United States. On the west coast of the United States, there is known a southward current 1402 initiating as the north Pacific drift and as it passes California is referred to as the California Coastal current. Other important currents include and are not limited to the Peru/East Australian current 1403, the Brazilian current/Benguela current 1404, the west wind drift 1405, the West Australian current 1406, the Kuroshio current 1407 and the North Atlantic drift 1408. These strong currents are known and have the potential to generate a considerable amount of power but are presently not used for electricity generation but, presently, are not believed to be used for power generation. (Also, predictable ocean tides cause water to flow upstream in ocean tributaries at high tide and downstream in ocean tributaries at low tide and may be more widely used for electric power generation.)
Referring to PRIOR ART FIG. 15A and FIG. 15B, there is shown a diagram of a typical hydroelectric power plant. A first step in harnessing water energy in this means is to build a dam 1510 to create a pressure head that is proportional to the depth of the water backed up by the dam. The backed-up water is represented by reservoir 1503. At the base of the dam 1510, there may be intake gates 1501 which allow water that has been compressed by the head to flow through a penstock 1516 to powerhouse 1505 which is one of many such powerhouses 1505 that may be constructed along the width of a large dam. One powerhouse 1505 may comprise a generator 1514 and a turbine 1518 which outputs power to long distance power lines 1522. Once the water passes through the turbine, it is returned to the river 1520. Details of the generator and turbine are shown in FIG. 15B. A generator 1514 may comprise a stator 1525, a rotor 1528 where the rotor is turned by a turbine generator shaft 1530. The generator 1514 creates electric power at grid frequency which then feeds power grid 1522. The turbine 1518 may comprise a wicket gate 1532 for controlling the amount of water flow 1529 to the turbine 1518. The wicket gate 1532 allows water to flow through turbine rotor blades 1534 and then pass on downstream to the river 1520 that has been dammed.
Referring to FIG. 16A through FIG. 16D, a run-of-the-river turbine is shown which first appears in U.S. Pat. No. 8,485,933, FIGS. 11 and 12. Protector ribs 1111 (FIG. 11) have been moved from the input as shown in FIGS. 11(B) and 12(B) to protect the waterwheel 1608 as seen as protector ribs 1630 in present FIG. 16A and FIG. 16D extending from block 1605 to partially cover the waterwheel 1608. Protector ribs 1111 of FIG. 11(B) and protector ribs 1630-4, 1630-5 and 1630-6, newly shown in FIG. 16D may serve two purposes, to protect the water input to the waterwheel 1608 from large debris and to channel the water toward the waterwheel 1608. In FIG. 16A through FIG. 16D, water flow is seen approaching from the left and flows over a block 1605 via a ramp portion analogous to a penstock and then over the flat surfaced top of block 1605 to a hatch 1612 which may be spring-loaded (spring not shown) or sensor controlled and so self-regulating from a fully open position shown in FIG. 16A to a partially closed position shown in FIG. 16B to a fully closed position shown in FIG. 16C depending on the volume and speed of the water, the direction of water flow and the spring constant of a spring (not shown). For example, during flood conditions, the turbine of FIG. 16C may have its hatch 1612 fully closed. The spring constant may be selected to match the specific characteristics of a hatch lip, not shown, for catching water as it flows toward the rotor blades of the waterwheel 1608. FIG. 16D shows top views of protector ribs 1630-1 to 1630-6 and water guides or venturis 1630-4 and 1630-6 channeling the water to the base of the block 1605, the water flowing over the block 1605 and to the waterwheel 1608 protected by protector ribs 1630-1 to 1630-3 for generating power. In the present specification, all depicted embodiments of the present invention are not drawn to scale and are intended to depict concepts that may be utilized and sized differently in different applications such as shallow, fast rivers; deep, long rivers, ocean currents, tidal estuaries and the like. The number and location of protector ribs 1630 are exemplary only and not intended to be limiting. Also, the first number or numbers of a reference numeral denote where that identified component first appears. So, for example, block 1605 will be consistently labeled as such in the drawings with numbers which follow after FIG. 16A through FIG. 16D.
All of the above-identified patents and published applications are incorporated by reference herein as to their entire contents.
Even with the above-described improvements to wind, river and ocean turbine devices known from the above identified entities, patent applications and patents, there still remains a need in the art to provide further enhancements and improvements to, for example, scalability, efficiency, reliability and increased electrical power generation by means of further embodiments of turbines and generators for run-of-the-river and for ocean currents and tides.